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Q.

I’m working on a 1949 Series I. I’ve repaired the chassis and trial-fitted the body, springs and wheels. The fit is bad and the vehicle isn’t level.

The chassis doesn’t seem to have been made accurately from the factory. For instance, where holes are positioned for spring-eye bolts, they’re not in the same place on each side of the chassis. On one side, the hole is central in the welded-on washer and on the other it’s well off to the side of the welded-on washer.

Is it normal for a chassis to be so wrong? What am I going to do with my chassis?

J Westhouse, Newcastle upon Tyne

A.

Your chassis wasn’t ‘wrong’ originally (although tolerances for early vehicles were quite large). This is best explained by reference to original manufacturing techniques, shown in the Summer 1949 edition of Machinery journal (black-and-white photos, above).

Longitudinals were made in two stages. Side plates were positioned either side of a block with a shaped top, while the ‘bottom’ plate was pressed into the shape of the block (everything is upside-down at this stage).Edges were tack-welded, and so sides and bottom were created.

Next, this was clamped the right way up and placed on another block. Magnetic side blocks were swung in to keep the side plates vertical. The top plate was positioned and clamped, then tack-welded. After this, both sides were seam-welded simultaneously – a man working along each side – so any distortion would be equalised. Then the chassis side rails and crossmembers were placed in a jig and welded together. After this, drilling jigs were lowered over the chassis and holes for spring bolts etc were drilled.

If there had been any distortion of the chassis frame during construction it wouldn’t matter, because the springs would still be positioned correctly even if the chassis were a little out-of-position in relation to the mounting hole.

In other words, even if the chassis were a little distorted, the mounting holes would always be in the right place. Smaller body-mounting holes may be slightly out of position, and sometimes on the production line slots were filed in body panel holes to allow for fit. There was, of course, some fore-and-aft adjustment available at the bottom of the bulkhead, by means of packing tubes or washers.

So, everything did fit correctly originally. If things don’t fit now, the chassis must be distorted. This is common where extensive repairs have been done to an old chassis.

When I was working on the reconstruction of my 1948 chassis I built a jig: two massive girders spaced apart with substantial studding (threaded rod).

This base jig was measured carefully and levelled with a laser level. Then the chassis was placed on the jig upside down (the battery carrier had to be cut off to allow this to happen). Where the chassis touched the girders I cut holes in the chassis and drilled through, then bolted the chassis to the jig. Bolt-on sub-jigs took care of alignment of outriggers and rear crossmember. Only then did I cut off the bad bits and start work.

With a flat jig and dimensions checked from the workshop manual, it was easy to know if the chassis was ‘square’. It’s the only way to be sure: welding a chassis ‘loose’ will probably get near-enough results, but you may end up with serious distortion. The only way to be sure about alignment now is to put the chassis on a jig and measure it. Peter Galilee

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